When a ballpoint pen is sold in the form of a refill, a sealing coat has so far been formed at the point part of the tip by melting and solidifying a thermoplastic sticking agent for the purposes of preventing volatilization from the point part of the tip and drying, preventing an ink from leaking onto a surface with which the pen point is brought into contact, avoiding oxidation of the ink and metal members such as the tip which is exerted from the outside and protecting the point part of the tip from impact in the stages of transportation and distribution.
In particular, in the case of a water-based ink ballpoint pen, a sealing coat has been formed principally because of the reasons described above, but in the case of an oil-based ink ballpoint pen, no specific problems are involved in prevention of volatilization from the point of the tip because a mixed solvent of 2-phenoxyethanol and benzyl alcohol which have a low volatility is usually used, and therefore in general, a sealing coat is formed or not formed depending on a diameter of a ball.
Known as conventional sealing coats for a point part of a ballpoint pen tip are a sealing coat comprising an ethylene-vinyl acetate copolymer (EVA) as a thermoplastic sticking agent (Japanese Patent Application Laid-Open No. 85623/1978) and a sealing coat comprising a cellulose base polymer (Japanese Patent Application Laid-Open No. 178798/1982).
On the other hand, oil-based inks which are excellent in a writing performance and a drying property of drawn lines and do not cause strike-through, and which have not so far been available, have been developed in recent years by combining various solvents.
The above oil-based inks are volatile inks and have a problem on a sealing property at the point part of the tip because a solvent component and the like are liable to be volatilized from the point of the tip when a conventional sealing coat is used, and the problems that starving is caused at the beginning of writing and that writing feeling is damaged are brought about in a certain case.
There have already been known cap members having various structures which comprise a cap main body detachably fit on a tip side of a refill (ballpoint pen main body) for a ballpoint pen charged with a water-based ink for a ballpoint pen or a water-based gel ink for a ballpoint pen and a sealing member provided in the inside of the above cap main body, wherein the cap member is formed so that the sealing member described above covers the point of the tip when the above cap main body is mounted on the tip side of the ballpoint pen main body.
A water-based ink ballpoint pen and a water-based gel ink ballpoint pen are liable to be dried at a point of a tip as compared with an oil-based ink ballpoint pen, and a solvent component and the like are liable to be volatilized from the point of the tip, so that the point of the tip has to be covered with a sealing member.
Known as a water-based ink ballpoint pen having such structure as described above is, for example, a ballpoint pen in which a nitrile rubber having a Shore A hardness of Hs 5 to 36 is used as a sealing rubber for the cap member described above (for example, Japanese Patent Application Laid-Open No. 370491/2002 filed by the present applicant).
However, the cap member described in the foregoing document is used only for conventional water-based ink ballpoint pens and is not used for oil-based ink ballpoint pens having different ink compositions.
Since a mixed solvent of 2-phenoxyethanol and benzyl alcohol which have a low volatility is usually used in conventional oil-based ink ballpoint pens, no specific problems have been involved in prevention of volatilization from the point of the tip, and therefore the point of the tip does not have to be covered with a sealing member in a cap member.
On the other hand, oil-based inks which are excellent in a writing performance and a drying property of drawn lines and do not cause strike-through, and which have not so far been available, have been developed in recent years by combining various solvents.
The above oil-based inks are volatile inks and have a problem on a sealing property at the point part of the tip because a solvent component and the like are liable to be volatilized from the point of the tip when a conventional sealing coat is used, and the problems that starving is caused at the beginning of writing and that writing feeling is damaged are brought about in a certain case.
In light of the problems on the prior art described above, the present invention intends to solve them, and the first object thereof is to provide a refill for an oil-based ink ballpoint pen which can be surely formed a sealing coat at the point part of a tip without using a principal solvent and a thermoplastic sticking agent each conventionally used for an oil-based ink and inhibits an ink solvent from absorbing moisture from the outside and volatilizing with the passage of time and which inhibits starving at the beginning of writing after transportation and storage, protects a pen point and is excellent in making writing feeling soft and smooth. The second object thereof is to provide an oil-based ink ballpoint pen which inhibits starving at the beginning of writing as well as preventing a solvent from volatilizing from a pen point even if a specific oil-based ink having a volatilizing property is used and which is excellent in making writing feeling soft and smooth.